[Recurrence tendency and malignant transformation of pleomorphic adenomas].

Young patients and those with the stroma-rich variant of pleomorphic adenoma have an increased risk of local recurrence. Review of 98 patients with recurrent pleomorphic adenoma showed that the primary operation is nevertheless decisive for the further progress of the disease: incomplete tumour excision and enucleation of pleomorphic adenomas were responsible for tumour recurrence which may be multiple. Recurrence in turn favours the development of carcinoma within pleomorphic adenomas. Of 23 carcinomas, 20 developed within recurrent tumours. These 20 tumours comprised 16.9% of all recurrences observed. A mean time of 16 years relapsed after the primary operation before a carcinoma developed in the recurrence. Slow and protracted tumour growth were characteristic of those carcinomas that could be also demonstrated in the original tumour (0.9% of the group of non-recurrent tumours) with a mean time of 7 years before operation. Immediate tumour removal is therefore the best prophylaxis against carcinoma. In 19 patients we showed that local recurrence due to dissemination can be avoided by appropriate measures, even after intra-operative opening of the tumour capsule.